Class KHRDisplayReference

The existing semantics of EGLDisplay object lifetimes work well for applications in which one module manages all EGL usage, and in which EGL
displays are expected to remain available until application termination once they are instantiated. However, EGL does not provide reasonable semantics
in the case where applications rely on toolkit libraries which use EGL independently from the application itself.

This issue can be solved by adding a per-EGLDisplay reference counter which is incremented by Initialize calls. Resource destruction can
then be deferred until a corresponding number of Terminate calls is made. However, switching to this behavior universally could cause backwards
incompatibility problems with existing applications that assume a single eglTerminate will immediately free resources regardless of how many
times the display has been initialized.

We therefore must support both behaviors. A new attribute specified when the EGLDisplay is obtained will indicate whether or not reference
counting is enabled. If an application requests the EGLDisplay multiple times with different values for this attribute, two separate displays
will be returned. The one potential drawaback is that these displays will have independent resource spaces, so objects allocated from one cannot be
used by the other. However, the goal here is to support modules that access EGL independently. In such a use case, they are not likely to need to share
resources with another module, particularly one that uses a different method for accessing the display.